Abstract

Quantum probabilities are generated by quantum states. But if neither quantum states nor Born probabilities describe or represent physical reality, then how can we use them to explain what happens? An otherwise puzzling phenomenon is explained when it is seen to be just what one should have expected. In accepting quantum theory one takes it as one's guide in forming beliefs in statements about values of magnitudes (NQMC)s. Quantum theory
first licenses one to form degrees of belief only in certain (NQMC)s in a given situation, based on an assessment of the relevant degree of decoherence. A quantum state then advises adoption of specific degrees of belief in appropriately licensed (NQMC)s equal to Born probabilities. Given these beliefs, a corresponding statistical distribution of magnitude values will (almost always) be just what one would have expected. That is how we use quantum theory to explain statistical regularities, whether we know about these through experimental measurements or by observation of natural events. (It is, for example, how we can use quantum theory to explain violation of Bell inequalities without any "spooky" action at a distance).